The following disclosure statement is made pursuant to the Duty of Disclosure imposed by law and formulated in 37 CFR 1.56(a). No representation is hereby made that information disclosed herein in fact can be considered prior art, since 37 CFR 1.56(a) includes a materiality concept which depends somewhat on certain inevitably subjective elements including much likelihood and reasonableness. Inasmuch as a growing attitude appears to require citation material which may lead to a discovery of more pertinent material, though not necessarily being of itself pertinent, the following comments contain conclusions and observations which have only been drawn from or become apparent after conception of the subject invention or comparisons contrasting the subject invention or its merits against the background of later developments.
This invention relates generally to heat exchangers employing tube bundles for transferring heat between fluids flowing inside the tubes to surrounding fluid outside the tube surfaces.
Heat exchangers employing tube bundles surrounded by flowing fluid outside the tubes, including a commonly used configuration known as a shell-and-tube, presently utilize staggered flow baffles to improve external tube heat exchange. A typical heat exchanger of this type is disclosed and claimed in U.S. Pat. No. 3,426,841.
The shell side baffles utilized in this construction extend from the upper and lower portions of the exchanger shell with the predetermined portion of the tube bundle passing through alternate baffles spaced along the tube flow length, and spanning a portion of the internal flow cross-section of the exchanger shell. This configuration essentially converts the longitudinal shell side flow to what can be called tube cross flow, by 180 degree reversals of the shell side fluid flow as it passes from one baffle to the other.
Heat exchangers of this construction, while providing satisfactory heat exchange, suffer from substantial difficulties, primarily due to large pressure drops caused by the baffle induced flow reversals, and relatively short tube bundle life due to flow vibration induced by shell side fluid cross flow. It is well known to those skilled in the heat exchanger art that cross flow turbulence occurring at flow rates great enough to improve external heat exchange results in mechanical tube vibration which often results in tube failure at the highest stress point, perforation of the tube at its intersection with the baffle, or failure of tube heat exchanger tube sheet interface.
A known heat exchanger construction as disclosed in U.S. Pat. No. 4,127,165, aimed at solving these problems, utilizes a substantial number of rods internal of the heat exchanger shell disposed around the tube axis, creating a rectangular tube support matrix. Exchanger tubes passing through somewhat essentially square apertures in this matrix provide support through direct contact for longitudinal tubes. The matrix also acts to increase or generate turbulence in the shell side flow.
This rod supported heat exchanger construction, while demonstrating improved performance over the more common tube baffle construction, suffers from substantial flow related difficulties. The turbulent flow vortices induced by the rod presence can result in a considerable amount of rod vibration, with attendant failures due to tube perforation at the rod/tube surface interface.
It is therefore an object of this invention to overcome the difficulties encountered in the above described heat exchangers by providing a shell and tube heat exchanger having a distributed tube support contained in the tube bundle interstices.
It is a further object of this invention to provide an improved shell/tube heat exchanger by incorporation of a plurality of flow interrupters arranged in a matrix configuration, thereby insuring positive positioning of flow interrupters within the tube bundle interstices, external of the heat exchange surfaces.
It is yet an additional object of this invention to provide a method of enhancing shell side heat transfer and extending life of the heat exchange tubes through installation of a connected matrix of flow interrupters and tube supports.
It is a further object of this invention to provide a method of improving existing heat exchanger performance through installation of preassembled flow interrupter and tube support in a matrix configuration.